公知 is read as こうち (kouchi) and means well-known.
こうち
kouchi
こうちのじじつ
common knowledge
あいちようすいこうだん
Aichi Waterworks Corporation
くげ
Imperial Court
こうかい
opening to the public
こうめい
Komeito (Japanese political party)
こうりつ
public (institution)
こうせい
justice
こうげん
declaration
こうし
envoy
こうあん
public safety
こうしゃ
public corporation
おおやけ
public (use, matter, forum, etc.)